A breast composition information acquisition section acquires a mammary gland content ratio in each unit pixel in a breast region of a radiological image obtained by irradiating a breast of a subject with radiation. A noise reduction section acquires an index value indicating the size of a variance range of pixel values at each unit pixel position from the mammary gland content ratio of each unit pixel, performs a noise reduction process so that the level of noise reduction at a position of an attention pixel is low as the index value is small, and performs the noise reduction process so that the level of noise reduction at the position of the attention pixel is high as the index value is large.
